import { addClass, removeClass } from '@/utils/dom.js';

/*
class Transition {
  beforeEnter(el) {
    addClass(el, 'collapse-transition');
    if (!el.dataset) el.dataset = {};

    el.dataset.oldPaddingTop = el.style.paddingTop;
    el.dataset.oldPaddingBottom = el.style.paddingBottom;

    el.style.height = '0';
    el.style.paddingTop = 0;
    el.style.paddingBottom = 0;
  }

  enter(el) {
    el.dataset.oldOverflow = el.style.overflow;
    if (el.scrollHeight !== 0) {
      el.style.height = el.scrollHeight + 'px';
      el.style.paddingTop = el.dataset.oldPaddingTop;
      el.style.paddingBottom = el.dataset.oldPaddingBottom;
    } else {
      el.style.height = '';
      el.style.paddingTop = el.dataset.oldPaddingTop;
      el.style.paddingBottom = el.dataset.oldPaddingBottom;
    }

    el.style.overflow = 'hidden';
  }

  afterEnter(el) {
    // for safari: remove class then reset height is necessary
    removeClass(el, 'collapse-transition');
    el.style.height = '';
    el.style.overflow = el.dataset.oldOverflow;
  }

  beforeLeave(el) {
    if (!el.dataset) el.dataset = {};
    el.dataset.oldPaddingTop = el.style.paddingTop;
    el.dataset.oldPaddingBottom = el.style.paddingBottom;
    el.dataset.oldOverflow = el.style.overflow;

    el.style.height = el.scrollHeight + 'px';
    el.style.overflow = 'hidden';
  }

  leave(el) {
    if (el.scrollHeight !== 0) {
      // for safari: add class after set height, or it will jump to zero height suddenly, weired
      addClass(el, 'collapse-transition');
      el.style.height = 0;
      el.style.paddingTop = 0;
      el.style.paddingBottom = 0;
    }
  }

  afterLeave(el) {
    removeClass(el, 'collapse-transition');
    el.style.height = '';
    el.style.overflow = el.dataset.oldOverflow;
    el.style.paddingTop = el.dataset.oldPaddingTop;
    el.style.paddingBottom = el.dataset.oldPaddingBottom;
  }
}
*/

function transition() {
  return {
    beforeEnter(el) {
      addClass(el, 'collapse-transition');
      if (!el.dataset) el.dataset = {};
  
      el.dataset.oldPaddingTop = el.style.paddingTop;
      el.dataset.oldPaddingBottom = el.style.paddingBottom;
  
      el.style.height = '0';
      el.style.paddingTop = 0;
      el.style.paddingBottom = 0;
    },
  
    enter(el) {
      el.dataset.oldOverflow = el.style.overflow;
      if (el.scrollHeight !== 0) {
        el.style.height = el.scrollHeight + 'px';
        el.style.paddingTop = el.dataset.oldPaddingTop;
        el.style.paddingBottom = el.dataset.oldPaddingBottom;
      } else {
        el.style.height = '';
        el.style.paddingTop = el.dataset.oldPaddingTop;
        el.style.paddingBottom = el.dataset.oldPaddingBottom;
      }
  
      el.style.overflow = 'hidden';
    },
  
    afterEnter(el) {
      // for safari: remove class then reset height is necessary
      removeClass(el, 'collapse-transition');
      el.style.height = '';
      el.style.overflow = el.dataset.oldOverflow;
    },
  
    beforeLeave(el) {
      if (!el.dataset) el.dataset = {};
      el.dataset.oldPaddingTop = el.style.paddingTop;
      el.dataset.oldPaddingBottom = el.style.paddingBottom;
      el.dataset.oldOverflow = el.style.overflow;
  
      el.style.height = el.scrollHeight + 'px';
      el.style.overflow = 'hidden';
    },
  
    leave(el) {
      if (el.scrollHeight !== 0) {
        // for safari: add class after set height, or it will jump to zero height suddenly, weired
        addClass(el, 'collapse-transition');
        el.style.height = 0;
        el.style.paddingTop = 0;
        el.style.paddingBottom = 0;
      }
    },
  
    afterLeave(el) {
      removeClass(el, 'collapse-transition');
      el.style.height = '';
      el.style.overflow = el.dataset.oldOverflow;
      el.style.paddingTop = el.dataset.oldPaddingTop;
      el.style.paddingBottom = el.dataset.oldPaddingBottom;
    }
  }
}

export default {
  name: 'BcCollapseTransition',
  functional: true,
  render(h, {
    children
  }) {
    const data = {
      // 此种写法会报错，但在element与iview里同样的写法不会报错
      // on: new Transition()
      on: transition()
    };
    return h('transition', data, children);
  }
};

/* 以上代码是构建了如下组件
<transition
  v-on:before-enter="beforeEnter"
  v-on:enter="enter"
  v-on:after-enter="afterEnter"
  v-on:before-leave="beforeLeave"
  v-on:leave="leave"
  v-on:after-leave="afterLeave">
  <!-- ... -->
</transition> */
